jon lapook to tell us what we need to know about these new findings. >> reporter: today's study is worrisome news for the more than seven million americans who have taken chantix. a new analysis links the pill to a 72% increase in the risk of heart problems. johns hopkins dr. sonal singh led the research. >> it is causing the same problems we are trying to prevent, that's why it's not worth the risk. we need to prevent cardiac disease among smokers, not increase it. >> reporter: the review involves more than 8,000 patients. while a 72% increased risk sounds alarming, a companion editorial entitled "is it a heart breaker?" notice that heart problems are still rare, occurring in only about 1% of patients taking chantix. the drug maker pfizer questions the way the analysis was conducted. dr. gail walk well is vice president of medical affairs for pfizer. >> we will continue to do a more in-depth look as the f.d.a. is asking us to do. to date we have not seen evidence of important risks to the heart health of patients from chantix. >> reporter: in mid-june, the f.d.a. warned chantix might be lin